Which property describes the resistance of an object to changes in its motion?

The property that describes the resistance of an object to changes in its motion is mass. Mass is a measure of the amount of matter in an object and directly relates to its inertia, which is the tendency of an object to resist any change in its state of motion. The greater the mass of an object, the more force is required to change its velocity, whether that be starting to move, stopping, or changing direction.

For example, a heavy object has a larger mass compared to a lighter one, and therefore it will require a greater force to start moving or stop than the lighter object. This characteristic is a fundamental concept in physics, often encapsulated in Newton's first law of motion, which states that an object at rest will remain at rest, and an object in motion will continue in motion at a constant velocity unless acted upon by a net external force. Thus, mass plays a crucial role in determining how an object responds to applied forces.